Application of molecular cytogenetic techniques to characterize the aberrant Y chromosome arising de novo in a male fetus with mosaic 45,X and solve the discrepancy between karyotyping, chromosome microarray, and multiplex ligation dependent probe amplification.

We present a rare male fetus with karyotype of mosaic 45,X that comprises two types of aberrant Y chromosomes arising de novo (Yq12 deletion and isodicentric Yq11.22). Both types of the aberrant Y chromosomes lack the AZFc region which are expected to result in oligospermia but unaffected male external genitalia.